A precise measurement of a flight time for a radio signal between a first transceiver and a second transceiver is a delicate measurement problem. One way to determine the flight time is to precisely time the interval between sending the signal and receiving the signal. Since this measurement involves two transceivers with two different clocks, a problem to accurately determine the length of this time interval arises.
A solution to this problem is to use a master clock that is transmitted to the transceivers and used to determine the length of the time interval. Another solution disclosed in a scientific publication by Jiang et al. “An assymetric Double Sided Two-Way Ranging for Crystal Offset”, Signals, Systems and Electronics, 2007. ISSSE '07. International Symposium on, provides a method to assess the available precision by means of utilizing two transceivers with two crystal based oscillators. This method shows what kind of precision to expect for a measurement.
Yet another solution is disclosed in a conference paper “PinPoint: An Asynchronous Time-Based Location Determination System” by Moustafa Youssef et al. in the conference proceedings of “Mobisys 2006, Uppsala”. This solution involves determining a distance between nodes in a network by means of determining a round-trip travel time for a signal between different nodes in a network, wherein each node has a corresponding clock that is not synchronized.